ORGANIC SUBSTANCES AS PLANT FOOD 



227 



of aspartic and the related glutamic acids does not exceed 20 to 25 

 per cent. 



Asparagine, accordingly, is not the initial product of hydrolysis, 

 but the result of synthesis. This view received a final substantia- 

 tion through the experiments of Prianishnikov. On germinating 

 in solutions of ammonium salts, he observed the synthesis of 

 asparagine in seeds not only from the amino acids present during 

 germination, but also from ammonia supplied from without. In 

 this connection it is interesting to note that not all seeds bring 

 about this synthesis with equal ease. It proceeds readily in seeds 

 rich in non-nitrogenous reserves, such as the carbohydrates and 

 fats, for example, in the seeds of graminaceous plants. In seeds of 

 leguminous plants, in which there are large amounts of reserve 

 proteins, but the carbohydrate content is comparatively small, 

 asparagine can be synthesized from ammonium salts only when 

 calcium carbonate is supplied at the same time, which neutralizes 

 the free acid. But the seeds of lupine, which are very poor in non- 

 nitrogenous reserves, are unable to form asparagine from ammonia, 

 since the necessary carbohydrates are lacking. 



Prianishnikov's data illustrate the different capacities of seeds 

 for synthesizing asparagine from the absorbed ammonium com- 

 pounds. In the table are given amounts of asparagine, in milli- 

 grams, which formed in the dark in 100 seeds of each type of plants. 

 In the first case, germination was conducted in water; in the second 

 instance, in a solution of ammonium chloride; in the third, in a 

 solution of ammonium chloride with the addition of calcium car- 

 bonate. 



In the lupine there was a decrease of asparagine synthesis in the 

 presence of ammonium salts. But when these seeds were given 

 carbohydrates, that is, when they were allowed to germinate in 

 the light, an increase of asparagine syntheses in the presence of 



